Japanese Patent Laid-open publication No. 4-249385 proposed a prior art thermoelectric piece which comprises a thermoelectric semiconductor coated on its opposed faces respectively with Ni-layers for soldering connection with corresponding electrodes. The Ni-layer is selected to block interdiffusion of one or more elements of the thermoelectric semiconductor and a soldering material into each other in order to avoid lowering of thermoelectric characteristics over a long time of use. However, the Ni layer is found to give only a reduced adhesive strength to the thermoelectric semiconductor, which may result in disconnection of the circuit and lower reliability of the thermoelectric device.